More than 700 migrants are feared to have drowned this week in three separate ship wrecks in the Mediterranean Sea as they tried to reach Europe in smuggling boats, according to the U.N. refugee agency.

Around 100 of those migrants came from a smuggler’s boat that sank Wednesday, while another 550 are missing from a boat that capsized Thursday morning on its way from Libya.

Italian police arrested the captain of the second boat, identified as a 28-year-old Sudanese man, after survivors pointed him out.

A third ship, on Friday, sank with an unknown number of people onboard. Around 135 people were rescued from the boat along with 45 bodies, but many more people are still missing from the boat.

“The situation is chaotic, we cannot be sure of the numbers, but we fear up to 700 people may have drowned in three shipwrecks this week,” UNHCR spokesman Federico Fossi told AFP.

In total Friday, more than 1,900 migrants were rescued from boats in the Mediterranean in 16 different operations, according to the Italian Coast Guard.

The survivors of the shipwrecks were taken to the Italian port cities of Taranto and Pozallo, where they will be held while Italian authorities gather information from them. (VOA/AP/AFP/Reuters)